68k user RAM: Difference between revisions
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Revision as of 20:55, 7 October 2011
68k user RAM
Sometimes called "work RAM".
64KiB mapped in the 68k's memory space, from $100000 to $10FFFF (mirrored up to $1FFFFF on cartridge systems).
The range from $10F300 to $10FFFF is used by the BIOS functions and shouldn't be used as regular work RAM.
The MVS BIOS checks the entire RAM during boot by filling with $5555, reading back, filling with $AAAA, reading back and filling with a 16bit incremental value then reading back. If it encounters an error, it will lock-up after displaying the address where the error occured, and the read/write difference.
In CD systems, the 68k's RAM is used in the same way, but is located in part of the program DRAM instead of in separate static RAM chips (?).
Z80 user RAM
2KiB mapped in the Z80's memory space, from $F800 to $FFFF. Not automatically cleared.